Virtual machine communication

ABSTRACT

Two or more virtual machines may be co-located on a same physical machine, and the virtual machines may communicate with each other. To establish efficient communication, memory mapping information for respective virtual machines can be exchanged between the respective virtual machines. An instance of a virtualized network interface can be established, and a direct communications channel can be mapped between respective virtualized network interfaces. Data packet routing information can be updated, such that data packets transferred between two of more co-located virtual machines can be transferred using the virtualized network interface communications channel.

BACKGROUND

In a computing environment, a Virtual Machine Monitor (VMM) is a software program that can present a virtualized physical machine interface on top of which multiple Operating Systems, including unmodified user applications, can be run. A virtual machine may be an instance of an operating system that executes on the VMM. Virtual machines may be used to concurrently run two or more different operating systems on a single physical computer system, for example, to isolate test and beta versions of computer program modules, without affecting other systems on a computer system. Further, virtual machines may be used to separate storage on a computer system, in order to create isolated storage systems.

SUMMARY

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key factors or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

Two or more virtual machines (VMs) may be co-located on a same physical machine. Often, co-located VMs may need to communicate with each other. For example, a software module in one VM may use a service located in another co-located VM. Typically, this communication happens via network protocols, for both co-located and non-co-located VMs. In this way, for example, communication between co-located VMs can be inefficient when compared with communication between two processes in an operating system (OS) as the communication can traverse multiple software layers and involves data copies. As an example, when co-located VMs wish to communicate with each other, one VM makes a processor-intensive procedure call into the hypervisor (e.g., a hypercall), and a communication channel is run through the hypervisor to a second VM. In some systems, this communication may be routed through an intermediate VM (e.g., a device driver VM) that hosts the network device driver.

There are current systems that attempt to overcome these issues. For example, one technique (e.g., Xen Split Drivers in Xen VMM: K. Fraser, Safe hardware access with the Xen virtual machine monitor, OASIS, October 2004.) supports a restricted inter-VM communication path using a virtualized Ethernet interface. However, this technique also incurs expensive copying of data and hypercalls, as well as involving a device driver VM in the critical path. Other techniques either use data packet snooping and copying (e.g., Xen Loop: J. Wang, A Transparent High Performance Inter-VM Network Loopback, HPDC, Boston, Mass., June 2008.), which is processor-intensive; a socket-like interface (e.g., Xen Socket: X. Zhang, A High-throughput Interdomain Transport for VMs; Middleware 2007, November 2007, Newport Beach, Calif.), which is highly intrusive and not transparent to applications; or a communication mechanism (e.g., XWay, K. Kim, Inter-domain socket communications supporting high performance and full binary compatibility on Xen; VEE 2008.) that works only for a specific network protocol (at the data transport layer), which is neither a general solution, nor an appealing one from a software design perspective. It may be desirable to have a technique and system for communicating between co-located VMs that is performant (e.g., provide high throughput and low latency), transparent (e.g., provide a transparent interface that mitigates modification of guest OS subsystems and user applications), non-intrusive (e.g., implementable without having to modify the guest OS or hypervisor sources), and dynamic (e.g., an ability to be enabled or disabled without having to disrupt execution of a VM).

Techniques and systems are disclosed herein for communicating between two or more co-located VMs. The techniques and systems comprise, among other things, efficient exchange of information between two or more VMs, for example, co-located on a same physical machine. Co-located VMs mutually can share respective physical memories, for example, in a read-only manner prior to actual communication. In this example, rather than copying data for communication, pointers to data are transferred between VMs. The sharing of VM memories can, for example, lead to an efficient communication channel between co-located VMs, without utilizing intermediate VMs. Further, to facilitate typical network protocol communications between applications in co-located VMs, a communication channel is exported as an instance of a virtualized network interface. Routing information can be updated for packet data, such that data packets that are transferred between co-located VMs can be sent using the virtualized network interface. As an example, Internet Protocol (IP) routing tables can be updated in a TCP/IP stack of the respective VMs with IP information, which enables data transfer across the direct communications channel between VMs. In this example, the update to the routing table can happen after establishing the virtualized network interface.

To the accomplishment of the foregoing and related ends, the following description and annexed drawings set forth certain illustrative aspects and implementations. These are indicative of but a few of the various ways in which one or more aspects may be employed. Other aspects, advantages, and novel features of the disclosure will become apparent from the following detailed description when considered in conjunction with the annexed drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of one embodiment of virtual machines.

FIG. 2 is a flow diagram of an exemplary method for efficiently communicating between two or more virtual machines co-located on a same physical machine.

FIG. 3 illustrates one embodiment of the exemplary method for efficiently communicating between two or more virtual machines co-located on a same physical machine.

FIG. 4 is an illustration of one embodiment an exemplary method for translating packet data from a first OS-specific packet data structure to a second OS-specific packet data structure.

FIG. 5 is an illustration of one embodiment an exemplary method for utilizing a membership mechanism for determining membership status of co-located VMs.

FIG. 6 is a component block diagram of an exemplary system utilizing an embodiment of an exemplary computer program module.

FIG. 7 is a component block diagram of an exemplary system using another embodiment of the exemplary computer program module.

FIG. 8 is a component block diagram of an exemplary system for communicating between two or more virtual machines co-located on a same physical machine.

FIG. 9 is an illustration of an exemplary computer-readable medium comprising processor-executable instructions configured to embody one or more of the provisions set forth herein.

DETAILED DESCRIPTION

The claimed subject matter is now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the claimed subject matter. It may be evident, however, that the claimed subject matter may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing the claimed subject matter.

Embodiments described herein relate to techniques and systems for facilitating efficient communication between two or more virtual machines co-located on a same physical machine.

FIG. 1 is an illustration of one embodiment 100 of virtual machines. In this embodiment 100 a single physical computer system 102 (e.g., a personal desktop computer) may contain one or more instantiations of a virtual machine, such as virtual machine 1 106, virtual machine 2 116, virtual machine 3 126, etc. Virtual machines, for example, may allow multiplexing of the underlying physical computer. Two or more virtual machines may be installed on a computer system in order to isolate software modules or operating systems. In this example, a programmer may wish to isolate the modules so that a beta test of the software can be run in a particular operating system on the computer, isolated from the rest of the system.

In this embodiment 100, the computer system 102 has a software layer called a virtual machine monitor 104 (hypervisor) installed thereon, which provides a virtualization platform and may be used to manage and monitor the one or more instantiations of virtual machines (e.g., 106, 116, 126, etc.) on the computer 102. In this example, the hypervisor 104 is installed directly on the native hardware of the computer 102; however, hypervisors may also be installed as a software layer in a native operating system, known as a host operating system.

In this embodiment 100 the hypervisor 104 has three instantiations of virtual machines (e.g., 106, 116, 126) installed thereon. Respective virtual machines can contain a different or a same operating system, such as operating system 1 108, operating system 2 118, operating system 3 128, etc. (e.g., some of which may be the same or different operating systems) and various program applications, such as a first set of program applications 110, a second set of program applications 120, a third set of program applications 130, etc. (e.g., where some of the program applications may be the same or different applications). As described above, the operating systems and applications run substantially isolated from the other virtual machines co-located on the same physical machine 102. Respective virtual machines communicate directly with the hypervisor 104, which in-turn, communicates with the respective virtual machines. Therefore, in this example, in order for the virtual machines to communicate with each other, messages will first pass through and be managed by the hypervisor 104, which may not be an efficient technique for virtual machine communication.

FIG. 2 is a flow diagram of an exemplary method 200 for efficiently communicating between two or more virtual machines co-located on a same physical machine. The exemplary method 200 begins at 202 and involves establishing a communication channel between co-located VMs, at 204. For example, a direct communications channel can be established between respective co-located VMs, without routing calls through the hypervisor.

FIG. 3 illustrates one embodiment 300 of the exemplary method 200 for efficiently communicating between two or more virtual machines co-located on a same physical machine. At 204 in the embodiment 300, the establishment of a communication channel between co-located VMs can involve using a rendezvous/discovery mechanism (e.g. a generic term referring to a synchronization process/mechanism that uses a system call to allow two processes to synchronize to exchange data) to find a co-located VM, at 312. At 314, a metadata is created that is shared between the co-located VMs. As an example, a shared metadata segment can be created 314 during an establishment of a connection between a new instantiation of a VM and one or more existing VMs.

At 316, the shared metadata segment may be used to establish a communication channel between the co-located VMs. For example, the metadata segment 316 may be used for signaling and sharing information between the co-located VMs. In this example, the metadata segment can be established 314 using the rendezvous mechanism between VMs 312. The rendezvous mechanism can be implemented using a hypervisor-specific associated database (e.g., a key-value database). Further, in this example, rendezvous/discovery mechanism 312 can proceed in an asynchronous, event-driven manner to allow for a VM to establish a connection with multiple VMs substantially concurrently.

Turning back to FIG. 2, at 206, memory mapping information (e.g., pointers pointing to specifically identified memory segments in a virtual machines physical memory, which may contain specifically identified portions of data) is exchanged between one or more co-located virtual machines. For example, the memory pointers of a first VM can be transferred to a physical memory of a second VM. In one embodiment, the exchanging of memory mapping information occurs prior to data transfer between VMs. In this embodiment, when a first VM transfers data to a second VM, the first VM can pass pointers to the data to the second VM, rather than performing a processor-intensive technique of copying the data. Additionally, as an example, physical memory of the first VM can be mapped into the second co-located VM's memory address spaces, prior to data transfer, in a read-only manner. In this example, the read-only manner mitigates an implementation bug causing the first VM to overwrite the second VM's memory. Also, in this example, if the first VM's memory is mapped into the second VM, resource costly calls to a hypervisor when mapping memory dynamically can be avoided.

In the embodiment 300 of FIG. 3, the exchanging of memory mapping information between virtual machines (VMs) 206, can involve the participating VMs exchanging information needed for mapping the memory of a first VM to a second VM over the metadata segment, at 318. At 320, memory mapping pointers from the first VM can be mapped into the memory of the second VM using hypercalls through the hypervisor. In this way, for example, once the first VM's memory has been exchanged and mapped, the second VM can have direct access to information stored in the first VM's memory.

Once again turning back to FIG. 2, in the exemplary method 200, at 208, an instance of a virtualized network interface in one or more virtual machines (VMs) is established. Establishing a virtualized network interface (VNI) in a VM, for example, may allow for a transparent direct communications channel to be established directly between VNIs in respective VMs. In one embodiment, establishing a virtualized network interface can be performed by installing a software module that performs network interface tasks (e.g., communication with other elements on the network), without using a hardware network interface device (e.g., instead using a native communication layer in a virtual machine).

In embodiment 300 of FIG. 3, at 208, an operating system (OS)-specific interface, corresponding to a network interface driver, is established in the VM 322. This mechanism can create an instance of a virtualized network interface device in the VM. As an example, the VNI in the VM can be presented as a network device (e.g., Ethernet interface) to the applications in the VM. Presentation in this manner may allow for a transparent communications channel to be established between co-located VMs, using the VNI.

In this embodiment, unlike in existing systems, signaling between VMs does not utilize interrupts, which require processor-intensive hypercalls. In one example, signaling between VMs may be implemented by polling on shared memory counters, using a processor core dedicated for communication. In another example, an efficient interrupt mechanism that avoids hypercalls may be used. In this example, a source VM can control the scheduling of a destination VM (e.g., a VM can schedule a signal processing thread in the destination VM as part of signaling the VM). It will be appreciated that, while the first example of signaling over a communications channel may be preferable due to its less intrusive nature, the techniques and systems, described herein, are not limited to a particular signaling mechanism.

In the exemplary method 200 of FIG. 2, at 210, data routing information is updated, such that data packets transferred between VMs is sent using respective VNIs. After a communications channel has been established between co-located VMs, for example, data packets destined to and from the VMs should be routed through the respective VNIs in order to take advantage of the direct communication channel.

In embodiment 300 of FIG. 3, at 210, the routing information is updated by updating the routing information in an Internet protocol (IP) routing table in a TCP/IP stack of the respective VMs, so that data packets destined to a VM are routed through the respective VNI, at 324. As an example, in order to update the IP routing table an IP address of the respective VM should be known. This information is typically available through the hypervisor. In this example, the available IP address information for respective co-located VMs can be used to update the IP routing table in the TCP/IP stack of respective VMs.

Having updated the routing information, the exemplary method 200, in FIG. 2, ends at 212.

In one aspect, as described above, a VM's memory is mapped a priori, for example, to avoid copying data. Further, polling is employed rather than interrupts, for example, to avoid hypercalls. Additionally, for example, in order to facilitate transparency to applications, the communications channel technique exports a standard network device interface. As a result, in this aspect, OS-specific packet data structures may be used in data paths.

In one embodiment, two VMs running different OSs (as in FIG. 1) can be made to communicate using the aforementioned techniques. In this embodiment, in a send data path, source OS-specific packet data structures can be packed into an OS-independent shared memory communications format, in a zero-copy manner (e.g., without making a copy). Similarly, in this embodiment, in a receive data path, the OS-independent shared memory communications format can be assembled into a destination OS-specific packet data structure. The data in the destination OS-specific packet data structure, for example, can then be delivered to a destination OS through the VNI.

FIG. 4 is an illustration of one embodiment 400 of an exemplary method for translating packet data from a first OS-specific packet data structure to a second OS-specific packet data structure. As an example, translating of OS-specific packet data may be needed if a first VM utilized a different OS than a second VM, and the respective VMs were attempting to transfer data between each other. In this example, different communications protocols (e.g., from different OSs) can use different conventions for distinguishing between elements of the packet data and formatting of the data. Therefore, a method can be used to translate between the different conventions used by different protocols, for example.

At 402, a source OS-specific packet data structure is mapped to a generic (e.g., independent of OS) packet data structure using memory mapping pointers. At 404, source OS-specific packet data structure is packed into an OS-independent shared memory communications format. As an example, during the initial memory mapping, memory mapping pointers are created, which may be used to pack memory mapping information into an OS-independent shared memory communications format.

At 406, destination OS-specific packet data structure mapping information can be extracted from the OS-independent shared memory communications format, using memory mapping pointers, for example, created during the memory mapping process. At 408, the destination OS-specific packet data structure mapping information can be packed into a destination OS-specific data structure. As an example, the destination OS-specific packet data structure can be delivered to an OS on the destination VM. As a result, the original source OS-specific packet data has been translated into destination OS-specific packet data, and may now be utilized by the destination VM.

In another aspect, it may be desirable to identify instantiations of VMs running on a physical machine, in order to enable dynamic creation and removal of the aforementioned communications channel between VMs. In this aspect, for example, it may be desirable to determine when a VM is created, resumed, or migrated onto the physical machine. Further, for example, it may also be desirable to determine when a VM is destroyed, suspended or migrated out of a physical machine.

In one embodiment, when a VM is instantiated on the physical machine, new connection channels can be established between the new instantiated VM and co-located VMs. In this embodiment, a membership mechanism can be used to determine if a VM has been new instantiated. As an example of the membership mechanism being used to determine if a VM has been newly instantiated, an associated array database (e.g., one aspect of a membership mechanism that utilizes a key-value pair), supported by the hypervisor, can be used in a generic manner to determine membership. In this example, one or more VMs already located on the physical machine can poll the database or subscribe to notifications from the database using a specified key. When a VM is created on, resumed or migrated into the physical machine it can update the key with a specified value. In this way, for example, a notification to the co-located VMs can be triggered, which in turn, can trigger connection establishment between the co-located VMs.

In another embodiment, VM destruction, suspension or migrating out of a physical machine may be monitored using a heartbeat check. In this embodiment, for example, membership status of co-located VMs can be determined by having respective VMs perform periodic heartbeat checks against co-located VMs. In this example, if a VM has been destroyed, suspended or migrated out, the heartbeat check would fail. A failed heartbeat check can then trigger connection dismantling between a lost VM and the co-located VMs.

FIG. 5 is an illustration of one embodiment 500 an exemplary method for utilizing a membership mechanism for determining membership status of co-located VMs. At 502, an associated array database (e.g., a key-value pair store) is used to notify respective VMs of key value updates. At 504, a new co-located VM is added to the physical machine, which triggers establishment of a local virtual network interface (VNI). As described above, for example, when a new VM is instantiated on the physical machine a key in the database can be updated with a specified value. In this example, when the key value is updated, notifications can be sent to the existing co-located VMs, which can trigger establishment of a communications channel between the one or more existing co-located VMs and the new VM.

At 506, a heartbeat check against the co-located VMs is used to monitor membership status of respective VMs. As described above, for example, if a co-located VM has been destroyed, suspended or migrated out, the heartbeat check would fail. In this example, this can trigger dismantling of respective connections between a lost VM and the remaining co-located VMs. Further, in this aspect, dismantling of a connection may involve removing an instance of a virtualized network interface, which corresponds to the endpoint of a connection the lost VM, for example. Additionally, in this example, dismantling can involve removal of memory mapping information for the lost VM for the remaining co-located VMs.

A computer program module may be devised for communicating between two or more virtual machines co-located on a same physical machine. FIG. 6 is a component block diagram of an exemplary system 600 utilizing an exemplary computer program module 608 devised to facilitate communication between two or more virtual machines co-located on a same physical machine. In this embodiment the exemplary module 608 (e.g., a memory mapping network module (MMNET)) comprises a communication channel discoverer 622 configured to initiate a communication channel 624 between a local virtual machine (VM) 602 and one or more co-located VMs 604. As an example, during an initial connection establishment between co-located VMs, an initial control configuration path 624 can be used for initial discovery and configuration of the connection. In this example, the initial control configuration path 624 may be arbitrated by the virtual machine monitor (VMM) 606.

The exemplary computer program module 608 further comprises a memory mapper 626 configured to share memory mapping information between two or more co-located VMs. As an example, when a VM is instantiated on a physical machine with one or more existing co-located VMs, the local memory mapper 626 can transfer memory map information of the local VM's memory to the existing co-located VMs. Further, in this example, memory mappers located on existing co-located VMs can transfer memory map information of their respective VMs memories to the new instantiated VM. In the embodiment 600 memory map information can be transferred using the initial control configuration path 624 initiated by the communication channel discoverer 622.

The exemplary computer program module 608 further comprises a virtualized network interface connector 614 configured to establish a communications channel 620 between two or more virtualized network interfaces 616 and 618 on respective co-located VMs 602 and 604. As an example, the virtualized network interface connector 614 can map an endpoint of a local connection to a virtualized network interface device 616, which is in turn connected to the virtualized network interface device 618 on a co-located VM 604. In this way, the co-located VMs 602 and 604 may communicate directly across direct communications channel 620, instead of using the initial control configuration path 624 through the VMM 624.

The exemplary computer program module 608 further comprises an Internet Protocol (IP) routing updater 628 configured to update IP routing information, such that data transferred between two or more co-located VMs is routed through the local VM's virtualized network interface device 616. In this embodiment, for example, the IP routing updater 628 may update an IP routing table 630 located in a TCP/IP stack 610 of the local VM 602. In this example, the routing table 630 can be updated with the IP address information so that data packet traffic is routed through the local virtualized network interface device 616, using the direct communications channel 620.

FIG. 7 is a component block diagram of an exemplary system 700 using another embodiment of the computer program module 708. In this embodiment, the computer program module 708 also comprises a membership determination component 734 configured to determine membership status of co-located virtual machines 602 and 604. As an example, the membership determination component 734 can identify when a VM is initiated, resumed or migrated onto a physical machine, and send notifications to co-located VMs. In this example, the identification of a new member VM can trigger connection initiation between the VMs. Further, for example, the membership determination component 734 can perform a heartbeat check against co-located VMs to identify whether a co-located VM has been destroyed, suspended or migrated out. In this example, if the heartbeat check fails against a VM, connection dismantling can be triggered.

In this embodiment, the computer program module 708 also comprises a data translator 732 configured to translate packet data from a first operating system (OS)-specific data packet structure to a second OS-specific data packet structure. As an example, respective co-located VMs 602 and 604 may have a different OS, and may use an OS-specific data packet structure when sending and receiving information across the direct communication channel 620. In this example, the data translator 732 can be used to map a source OS-specific data packet structure to a generic OS-independent data format, and send a packet across a send path in the direct communication channel 620. Further, in this example, the data translator 732 can be used to map the generic OS-independent data format packet to a destination OS-specific data packet structure in a receive path of the direct communication channel 620.

In this embodiment, the computer program module 708 also comprises a virtual machine connection dismantler 736 configured to remove a connection 620 between two or more co-located virtual machines 602 and 604 when an instantiation of a co-located VM 602 is removed. As an example, when a VM is destroyed, suspended or migrated out, the loss of the VM can trigger the virtual machine connection dismantler 736 to remove the connection 620. Removal of the connection 620, for example, can involve removal of memory mapping information of the removed VM 602 from other co-located VMs 604. Connection removal may also trigger removing the mapped endpoint of the local connection from the virtualized network device 616, for example.

A system may be devised for communicating between two or more virtual machines co-located on a same physical machine. FIG. 8 is a component block diagram of an exemplary system 800 for communicating between two or more virtual machines co-located on a same physical machine. The exemplary system 800 comprises a memory mapping communicator 810 configured to exchange virtual machine (VM) memory mapping information between two or more co-located virtual machines 804. As an example, when a VM is newly instantiated on a physical machine, the memory mapping communicator 810 can exchange its local physical memory mapping information with existing co-located VMs. It will be appreciated that, while the exemplary system 800 illustrates the memory mapping communicator 810 as located in a specific location, the system described herein is not limited to having the memory mapping communicator 810 located at that position.

The exemplary system 800 further comprises a virtualized network interface 808 on a local virtual machine 804 configured to communicate with one or more co-located virtualized network interfaces 808 of co-located VMs 804. As an example, the virtualized network interfaces 808 may be presented as a network Ethernet interface in a communications layer 820 on the VM 804. In this way, for example, the virtualized network interface 808 can directly communicate with other virtualized network interfaces 808 on co-located VMs 804.

The exemplary system 800 further comprises a virtualized network interface communications channel 814 between two or more co-located virtual network interfaces 808 on co-located VMs 804. As an example, a direct communications channel 814 can be mapped between local virtualized network interfaces 808 that can enable the co-located VMs 804 to communicate directly, and reduce a need to communicate across a hypervisor 806, using a computationally expensive hypervisor channel 812.

The exemplary system 800 further comprises a virtual machine packet data router 816 configured to route data packets transferred between two or more VMs using the virtualized network interface communications channel 814. As an example, the virtual machine packet data router 816 can be an Internet Protocol (IP) routing table located in a TCP/IP stack 818 of the local VM 804, which has been updated with IP information such that data will be transferred using the local virtualized network interface 808, across the virtualized network interface communications channel 814.

In one aspect, a system for communicating between two or more virtual machines co-located on a same physical machine may comprise an operating system (OS)-specific packet data structure translator, configured to translate packet data from a first OS-specific structure to a second OS-specific structure. In this way, for example, if co-located VMs are utilizing a different OS, source OS-specific data may be mapped to a generic OS-independent format in a send path, and the generic OS-independent format may be mapped to destination OS-specific data.

In another aspect, a system for communicating between two or more virtual machines co-located on a same physical machine may comprise a membership determination component, configured to determine membership status of co-located virtual machines. In this way, for example, co-located VMs can identify when a VM is initiated, resumed or migrated onto a physical machine. In this example, this may trigger an initiation of connections between the new VM and existing co-located VMs. Further, the membership determination component can perform a heartbeat check against co-located VMs to determine whether a VM has been destroyed, suspended or migrated out. In this example, if a VM is lost, the heartbeat may fail, which can trigger a dismantling of connections between the lost VM and the co-located VMs.

Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

It will be appreciated that processes, architectures and/or procedures described herein can be implemented in hardware, firmware and/or software. It will also be appreciated that the provisions set forth herein may apply to any type of special-purpose computer (e.g., file server, filer and/or storage serving appliance) and/or general-purpose computer, including a standalone computer or portion thereof, embodied as or including a storage system. Moreover, the teachings herein can be adapted to a variety of storage system architectures including, but not limited to, a network-attached storage environment and/or a storage area network and disk assembly directly attached to a client or host computer. Storage system should therefore be taken broadly to include such arrangements in addition to any subsystems configured to perform a storage function and associated with other equipment or systems.

The operations herein described are exemplary and imply no particular order. Further, the operations can be used in any sequence when appropriate and can be partially used (e.g., not all actions may be necessary). It should be understood that various computer-implemented operations involving data storage may comprise manipulation of physical quantities that may take the form of electrical, magnetic, and/or optical signals capable of being stored, transferred, combined, compared and/or otherwise manipulated, for example.

Another example involves computer-readable media comprising processor-executable instructions configured to implement one or more of the techniques presented herein. Computer readable media is intended to comprise any mechanism that can store data, which can be thereafter, be read by a computer system. Examples of computer readable media include hard drives (e.g., accessible via network attached storage (NAS)), Storage Area Networks (SAN), volatile and non-volatile memory, such as read-only memory (ROM), random-access memory (RAM), EEPROM and/or flash memory, CD-ROMs, CD-Rs, CD-RWs, DVDs, cassettes, magnetic tape, magnetic disk storage, optical or non-optical data storage devices and/or any other medium which can be used to store data. Computer readable media may also comprise communication media, which typically embodies computer readable instructions or other data in a modulated data signal such as a carrier wave or other transport mechanism (e.g., that has one or more of its characteristics set or changed in such a manner as to encode information in the signal). The computer readable medium can also be distributed (e.g., using a switching fabric, such as used in computer farms) over a network-coupled computer system so that computer readable code is stored and executed in a distributed fashion.

Another embodiment (which may include one or more of the variations described above) involves a computer-readable medium comprising processor-executable instructions configured to apply one or more of the techniques presented herein. An exemplary computer-readable medium that may be devised in these ways is illustrated in FIG. 9, wherein the implementation 900 comprises a computer-readable medium 908 (e.g., a CD-R, DVD-R, or a platter of a hard disk drive), on which is encoded computer-readable data 906. This computer-readable data 906 in turn comprises a set of computer instructions 904 configured to operate according to the principles set forth herein. In one such embodiment, the processor-executable instructions 904 may be configured to perform a method 902 for managing a cluster of data storage devices comprising a VIF, such as the method 200 of FIG. 2, for example. Many such computer-readable media may be devised by those of ordinary skill in the art that are configured to operate in accordance with the techniques presented herein.

The foregoing description has been directed to particular embodiments. It will be apparent, however, that other variations and modifications may be made to the described embodiments, with the attainment of some or all of their advantages. Specifically, it should be noted that one or more of the principles set forth herein may be implemented in non-distributed file systems. Furthermore, while this description has been written in terms of separate remote and support systems, the teachings are equally suitable to systems where the functionality of the remote and support systems are implemented in a single system. Alternately, the functions of remote and support systems may be distributed among any number of separate systems, wherein respective systems perform one or more of the functions. Additionally, the procedures, processes and/or modules described herein may be implemented in hardware, software, embodied as a computer-readable medium having program instructions, firmware, or a combination thereof. Therefore, it is the object of the appended claims to cover all such variations and modifications as come within the spirit and scope of the disclosure herein.

As used in this application, the terms “component,” “module,” “system”, “interface”, and the like are generally intended to refer to a computer-related entity, either hardware, a combination of hardware and software, software, or software in execution. For example, a component may be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program, and/or a computer. By way of illustration, both an application running on a controller and the controller can be a component. One or more components may reside within a process and/or thread of execution and a component may be localized on one computer and/or distributed between two or more computers.

Moreover, the word “exemplary” is used herein to mean serving as an example, instance, or illustration. That is anything described herein as “exemplary” is not necessarily to be construed as advantageous over other aspects or designs. Also, unless specified to the contrary, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or”, and the articles “a” and “an” are generally to be construed to comprise “one or more”. Furthermore, to the extent that the terms “includes”, “having”, “has”, “with”, or variants thereof are used, such terms are intended to be inclusive in a manner similar to the term “comprising”.

Also, although the disclosure has been shown and described with respect to one or more implementations, equivalent alterations and modifications will occur to others skilled in the art based upon a reading and understanding of this specification and the annexed drawings. The disclosure includes all such modifications and alterations and is limited only by the scope of the following claims. In particular regard to the various functions performed by the above described components (e.g., elements, resources, etc.), the terms used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (e.g., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary implementations of the disclosure. 

What is claimed is:
 1. A method for facilitating communication between a first virtual machine and a second virtual machine located on a physical host, comprising: establishing a communication channel between the first virtual machine and the second virtual machine utilizing a shared metadata segment; transferring, utilizing the shared metadata segment, a first physical memory map of the first virtual machine to a second physical memory of the second virtual machine, the first physical memory map comprising at least one memory pointer to a first physical memory of the first virtual machine; transferring, utilizing the shared metadata segment, a second physical memory map of the second virtual machine to the first physical memory of the first virtual machine, the second physical memory map comprising at least one memory pointer to the second physical memory of the second virtual machine, the second physical memory different than the first physical memory; and facilitating communication between the first virtual machine and the second virtual machine over the communication channel based upon at least one of the first physical memory map or the second physical memory map.
 2. The method of claim 1, the facilitating communication comprising at least one of: providing the first virtual machine with access, over the communication channel, to the second physical memory of the second virtual machine; or providing the second virtual machine with access, over the communication channel, to the first physical memory of the first virtual machine.
 3. The method of claim 2, comprising: providing at least one of the first virtual machine with read-only access to the second physical memory or the second virtual machine with read-only access to the first physical memory.
 4. The method of claim 1, the facilitating communication comprising: establishing direct communication between the first virtual machine and the second virtual machine without routing communication information through a virtual machine manager.
 5. The method of claim 1, the shared metadata segment comprising an initial control configuration path that is different than the communication channel.
 6. The method of claim 1, the facilitating communication comprising: utilizing a polling technique to signal communication over the communication channel.
 7. The method of claim 6, the utilizing a polling technique comprising: polling one or more shared memory counters.
 8. The method of claim 1, comprising: updating an internet protocol (IP) routing table in a TCP/IP stack.
 9. The method of claim 1, comprising: translating packet data from a first operating system-specific structure to a second operating system-specific structure; and sending the packet data, translated to the second operating system-specific structure, over the communication channel.
 10. The method of claim 1, the facilitating communication comprising: providing the first virtual machine with read-only access, over the communication channel, to the second physical memory of the second virtual machine.
 11. The method of claim 1, the facilitating communication comprising: providing the first virtual machine with access, over the communication channel, to a memory segment within the second physical memory of the second virtual machine based upon a memory pointer of the at one least memory pointer within the second physical memory map that points to the memory segment.
 12. The method of claim 1, comprising: specifying a first virtual machine membership for the first virtual machine within an array database.
 13. The method of claim 12, comprising: responsive to a failure of a heartbeat associated with the first virtual machine, updating the first virtual machine membership to create an updated first virtual machine membership.
 14. The method of claim 13, comprising: removing the communication channel based upon the updated first virtual machine membership.
 15. The method of claim 1, comprising: responsive to identifying an instantiation of a third virtual machine, creating a third virtual machine membership within an array database.
 16. The method of claim 15, comprising: providing notification to the first virtual machine of the third virtual machine membership for establishment of a second communication channel between the first virtual machine and the third virtual machine.
 17. The method of claim 1, the establishing a communication channel comprising: establishing a first virtualized network interface on the first virtual machine; and establishing a second virtualized network interface on the second virtual machine.
 18. The method of claim 17, comprising: configuring the first virtualized network interface and the second virtualized network interface to communicate over the communication channel.
 19. A non-transitory computer-readable medium comprising processor-executable instructions that when executed perform a method for facilitating communication between a first virtual machine and a second virtual machine located on a physical host, comprising: establishing a communication channel between the first virtual machine and the second virtual machine utilizing a shared metadata segment; transferring, utilizing the shared metadata segment, a first physical memory map of the first virtual machine to a second physical memory of the second virtual machine, the first physical memory map comprising at least one memory pointer to a first physical memory of the first virtual machine; transferring, utilizing the shared metadata segment, a second physical memory map of the second virtual machine to the first physical memory of the first virtual machine, the second physical memory map comprising at least one memory pointer to the second physical memory of the second virtual machine, the second physical memory different than the first physical memory; and facilitating communication between the first virtual machine and the second virtual machine over the communication channel based upon at least one of the first physical memory map or the second physical memory map.
 20. The non-transitory computer-readable medium of claim 19, the facilitating communication comprising at least one of: providing the first virtual machine with access, over the communication channel, to the second physical memory of the second virtual machine; or providing the second virtual machine with access, over the communication channel, to the first physical memory of the first virtual machine.
 21. The non-transitory computer-readable medium of claim 20, comprising: providing at least one of the first virtual machine with read-only access to the second physical memory or the second virtual machine with read-only access to the first physical memory.
 22. The non-transitory computer-readable medium of claim 19, the facilitating communication comprising: establishing direct communication between the first virtual machine and the second virtual machine without routing communication information through a virtual machine manager.
 23. The non-transitory computer-readable medium of claim 19, the shared metadata segment comprising an initial control configuration path that is different than the communication channel.
 24. The non-transitory computer-readable medium of claim 19, the facilitating communication comprising: utilizing a polling technique to signal communication over the communication channel.
 25. The non-transitory computer-readable medium of claim 24, the utilizing a polling technique comprising: polling one or more shared memory counters.
 26. The non-transitory computer-readable medium of claim 19, comprising: updating an internet protocol (IP) routing table in a TCP/IP stack.
 27. The non-transitory computer-readable medium of claim 19, comprising: translating packet data from a first operating system-specific structure to a second operating system-specific structure; and sending the packet data, translated to the second operating system-specific structure, over the communication channel.
 28. The non-transitory computer-readable medium of claim 19, the facilitating communication comprising: providing the first virtual machine with read-only access, over the communication channel, to the second physical memory of the second virtual machine.
 29. The non-transitory computer-readable medium of claim 19, the facilitating communication comprising: providing the first virtual machine with access, over the communication channel, to a memory segment within the second physical memory of the second virtual machine based upon a memory pointer of the at one least memory pointer within the second physical memory map that points to the memory segment.
 30. The non-transitory computer-readable medium of claim 19, comprising: specifying a first virtual machine membership for the first virtual machine within an array database.
 31. The non-transitory computer-readable medium of claim 30, comprising: responsive to a failure of a heartbeat associated with the first virtual machine, updating the first virtual machine membership to create an updated first virtual machine membership.
 32. The non-transitory computer-readable medium of claim 31, comprising: removing the communication channel based upon the updated first virtual machine membership.
 33. The non-transitory computer-readable medium of claim 19, comprising: responsive to identifying an instantiation of a third virtual machine, creating a third virtual machine membership within an array database.
 34. The non-transitory computer-readable medium of claim 33, comprising: providing notification to the first virtual machine of the third virtual machine membership for establishment of a second communication channel between the first virtual machine and the third virtual machine.
 35. A system for facilitating communication between a first virtual machine and a second virtual machine located on a physical host, comprising: a communication component configured to: establish a communication channel between the first virtual machine and the second virtual machine utilizing a shared metadata segment; transfer, utilizing the shared metadata segment, a first physical memory map of the first virtual machine to a second physical memory of the second virtual machine, the first physical memory map comprising at least one memory pointer to a first physical memory of the first virtual machine; transfer, utilizing the shared metadata segment, a second physical memory map of the second virtual machine to the first physical memory of the first virtual machine, the second physical memory map comprising at least one memory pointer to the second physical memory of the second virtual machine, the second physical memory different than the first physical memory; and facilitate communication between the first virtual machine and the second virtual machine over the communication channel based upon at least one of the first physical memory map or the second physical memory map.
 36. A system for facilitating communication between a first virtual machine and a second virtual machine located on a physical host, comprising: one or more processors; and memory comprising instructions that when executed by at least some of the one or more processors perform acts, comprising: establishing a communication channel between the first virtual machine and the second virtual machine utilizing a shared metadata segment; transferring, utilizing the shared metadata segment, a first physical memory map of the first virtual machine to a second physical memory of the second virtual machine, the first physical memory map comprising at least one memory pointer to a first physical memory of the first virtual machine; transferring, utilizing the shared metadata segment, a second physical memory map of the second virtual machine to the first physical memory of the first virtual machine, the second physical memory map comprising at least one memory pointer to the second physical memory of the second virtual machine, the second physical memory different than the first physical memory; and facilitating communication between the first virtual machine and the second virtual machine over the communication channel based upon at least one of the first physical memory map or the second physical memory map. 